Oil conserving apparatus for oil bath filter



July 10. 1956 c. J. GLANZER ETAL OIL CONSERVING APPARATUS FOR OIL BATH FILTER Filed March 29, 1952 2 Sheets-Sheet, 1

INVENTOR!)- CAAREWCE' 2' GLANZER Bydlqcaa A. BR/A'Ius 7A,m; /Jmd Arum/vars United States Patent OIL CONSERVING APPARATUS FOR OIL BATH FILTER Clarence J. Glanzer, Houston, Tenn, and Jacob K. Brixius, Par-ma, Ohio, assignors to Air-Maze Corporation, Cleveland, Ohio, a corporation of Delaware Application March 29, 1952, Serial No. 279,412 6 Claims. (Cl. 183-15 This invention relates to improvements in filters and more particularly to an oil conserving apparatus with an oil bath filter.

One of the objects of the present invention is to provide an oil conserving apparatus with an oil bath filter especially designed for the inlet of a free-unloading type gas compressor or other type gas utilizing devices with similar flow characteristics.

Another object of the present invention is to provide in an oil conserving apparatus of the type described the combination of an oil bath filter for filtering incoming gas during normal flow and means for conserving the oil by eliminating the oil loss caused by oil blow-back during reverse flow from a free-unloading type gas compressor.

Another object of the present invention is to provide in an oil conserving apparatus of the type describedabove, a dual purpose means for eliminating the oil from the carrier gas stream during reverse flow and for pre-filtering the incoming gas during normal flow before it reaches said oil bath filter.

Other features of this invention reside in the arrangement and design of the parts for carrying out their appropriate functions.

Other objects and advantages of this invention will be apparent from the accompanying drawings and description and the essential features will be set forth in the appended claims.

In the drawings,

Fig. 1 is an elevational view, partly in vertical longitudinal section, of an oil conserving apparatus with an oil bath filter;

Fig. 2 is an enlarged, horizontal sectional view through the oil eliminator means of the apparatus taken along the line 2-2 of Fig. 1;

Fig. 3 is an enlarged plan view of two adjacent flat layers of screen mesh, unwound from the spiral form in the upper part of Fig. 1, wherein each layer has substantially chevron-shaped crimps;

Fig. 4 is a top view of a portion of Fig. 3;

Fig. 5 is a view, similar to Fig. 1, but of a modified form of oil conserving apparatus with an oil bath filter;

Fig. 6 is an enlarged plan view of another form of oil eliminator means screen mesh material, similar to Fig. 3, but having diagonally inclined crimps.

While the present invention in an oil conserving apparatus might be adapted to various uses, we have chosen to show the same as applied to an oil bath filter and more particularly to show the oil conseiving apparatus with a conventional oil bath filter as usually applied to the inlet of a free-unloading type gas compressor or more specifically an air compressor. But it should be understood that'this composite device can be used with any gas utilizing device having similar flow characteristics although its use on a gas compressor will be described in detail hereinafter. Such a compressor, when it unloads, blows the gas or air back through the oil bath of the conventional oil bath filter causing an oil spray to be blown upwardly out of the normal inlet of the filter;

sor will follow the arrows in Fig. l.

2,753,951 Patented July 10, 1956,

2 This oil spray resembles a fountain and not only makes an untidy mess but also reduces the depth of the oil bath below its normal and safe operating level.

Various types of relief valves have been used in this location to prevent the blow-back of the oil. One such valve is shown in the U. S. Patent No. 2,548,374, entitled Relief Valve, granted April 10, 1951, to T. J. Janson. None of these relief valves have worked very satisfactorily since they take time to open and some oil is blown out in that time interval.

The present oil conserving apparatus with a conventional oil bath filter prevents blow-back of the oil when the compressor unloads and also offers very little resistance to the gas flowing into and out of the compressor. The present apparatus not only overcomes the difficulties mentioned above but also performs other desirable functions heretofore not obtained.

Figs. 1 and 2 disclose one form of this invention in an oil conserving apparatus with a conventional type oil bath filter.

Here, the incoming, normal flow of gas to the compres- In normal flow, the gas will enter the oil conserving apparatus through the inlet 10, will travel through the housing, and then will move through the outlet 11 into the gas compressor. When the compressor unloads, the gas will move in a reverse flow direction through the oil conserving apparatus and oil bath filter. The inlet 10 and the outlet 11 for normal flow will have their functions reversed during reverse flow. Then, the gas will move in a direction op posite to the arrows in Fig. 1.

The liquid wash filter or oil bath filter in Fig. 1 is one of the conventional type. A housing is provided with a cylindrical outer wall 12 and a cylindrical inner wall 13, each telescopically connected over a reduced diameter of an annular-shaped bottom member or bowl 14. This bowl 14 is substantially cup-shaped in cross section so that it and the walls 12, 13 can retain a bath of oil within; their annular shape. A coupling tube 15, adapted to connect to the gas compressor inlet, is telescoped into and. firmly attached to the central bore of the bottom member' 14. The filter is provided with a cap 16 having a depending skirt 16a, cylindrical in form and extending below the normal oil level 24.

The parts of the oil bath filter are held together as; a unit. An adapter member 18 is secured in a hole in the center of cap 16 by a resilient snap ring 23 squeezing, washer members 21, 22 against a shoulder on the adapter member 18. A stud 20 is pinned to the adapter member 18 and is threaded into a threaded hole in a web or spider 15a integrally formed in the coupling tube 15. One or more annular filter elements 25 are secured in the filter chamber between the bottom member 14 and cap 16 outside of the discharge tube 13 and inside of the depending skirt 16a. One form of filter element is composed of? foraminous screen mesh material. A cylindrical bafile: 26 is rolled into the screen mesh material 25 and engages: the bottom member 14. This bafile forces the incoming; gas to go upward through the oil filter element 25 afterit picks up oil under the skirt 16a so that efiicient andi thorough filtering is obtained.

The flow of gas through the oil conserving apparatus: and oil bath filter in the normal direction should be ap parent. The incoming gas enters the inlet 10 of the oil conserving apparatus, travels through a passageway in the apparatus housing into the inlet of the oil bath filter. This latter inlet takes the form of the annular passageway between the cylindrical outer wall 12 and the depending skirt 16a. The bottom of the housing is filled with oil or other suitable washing liquid to the level of the dot-dash line 24. The incoming gas stream passes beneath the depending skirt 16a taking up oil as it moves and then travels upwardly inside the skirt through the annular filter element 25. As the gas passes radially inwardly through the filter element, it is cleaned thereby and the oil is removed. Then, the gas is discharged from the apparatus through the normal outlet 11 into the gas compressor.

The term oil is used to mean any suitable liquid adhesive which may be carried by the gas stream during normal flow up into the filter elements to catch the dirt particles in the gaseous stream and to wash the same back into the bottom of the retaining bowl.

An oil eliminator means is provided in the flow path between the oil bath filter and the inlet of the apparatus to prevent oil and finely divided oil spray being exhausted through the normal inlet 10 during reverse flow. It includes a housing having a cylindrical outer wall 30 with a bell-mouthed bottom substantially the same diameter as the cylindrical outer wall 12. A sleeve adapter 31 is welded to wall 30 and telescopically engages the outer wall 12 and has in a circular groove in its outer surface an O-ring gasket 32 to seal the connection between the two walls. This construction permits the oil eliminator means to be lifted oil the oil bath filter when 43, 44 is unscrewed.

The oil eliminator means has two vertically spaced filter elements 33, 34 with their supporting structure. One form of suitable filter material is a foraminous screen mesh material such as disclosed in U. S. Patent No. 2,190,683 granted to Albert E. Schaaf, et al., February 20, 1940, and entitled Filter Means and Method of Making Same." This is illustrated in Fig. 6 and has diagonally inclined, oppositely directed crossing crimps in alternate layers wherein each crimp extends straight through for the vertical height of the screen mesh layer. Each of the filter elements 33 or 34 may be formed from concentric layers of the foraminous screen mesh material shown in Fig. 6, or the layers shown in Fig. 6 may be rolled upon themselves spirally in an ever-increasing radius until the proper annular form is constructed. The diagonal crimps will extend generally at an acute angle to or generally in the direction of the vertical stream fiow through the filter elements 33 and 34.

This foraminous screen mesh material may take other forms than that shown in Fig. 6 such as the chevron-shape in Fig. 3 or a Z-shape (not illustrated) wherein the adjacent downwardly directed bars of the 2 have about the same angle between them as the downwardly directed bars of the chevron in Fig. 3. In both of these latter two forms the crimps also extend generally in the direction of vertical stream fiow so that they will be of the selfdraining type with all of the passages between the crimps generally inclined downwardly.

The upper filter element 33 has larger effective flow passages than the lower element 34. This may be achieved, for example, by having the same number of wire meshes per inch in both filter elements but having smaller crimps (smaller in height) in the layers of the lower filter element 34 so that the passages are smaller, and in effect, a finer filter results.

These filter elements 33 and 34 are supported by and are bounded in their axial dimension (bottom and top in Fig. 1) by the expanded metal annular discs 35, 36, 37, 38. Equally spaced, spacer bars 39 are welded to or otherwise attached to the expanded metal disc 36, as. shown in Fig. 2. Thesespacers provide a vertical. air gap, as shown in Fig. 1', between the filter elements 33. and 3,4. The purpose of this air gap will be set forth in more detail hereinafter.

The filter elements 33, 34 are so constructed that they may be inserted into or removed from the. cylindrical outer wall 30as, a unit. A fastenermember 41 has a cylindrical tubular portion throughout its entire. length nd has flan es-- ntegrally form d. on. pposite: ends, to.

ecu e. he fil r. e am nts. 33. and 34i"therebetween.

Washer nacer memltersfl, 40 are utovidedbe ween.

the flanged ends and the filter elements. The unit is adapted to telescope into or out of the top of the cylindrical outer wall 30 and rests on an annular bottom stop 42 secured to the outer wall 30.

The housing of the oil conserving apparatus also has a top. A stem 43 is adapted to telescope into fastener member 41 and to thread into the adapter member 18 and has a wing grip 44 pinned to its upper end. A cap 46, adapted to cover the top of the cylindrical housing 30 is securely held in place by the stem 43 and wing grip 44. Apertures 30a are provided through the walls 30 to allow the incoming gas to enter the oil conserving apparatus. A snap ring 45 securely holds the filter elements 33, 34 against the bottom stop 42.

A bafiie means is located in the gas flow path between the oil eliminator means and the oil bath filter and includes the annular bafiie 50 with an inwardly and downwardly inclined lip. It also includes the bell bottom of housing outer wall 30 serving as a radially outward extension of battle 50 and covering the top of the annular fiow passageway formed by wall 12 and skirt 16a. This bafile means aids in the removal of the oil from the gas during reverse flow as will be described in more detail later in the specification. Bafiie 50 is formed integral with the previously described stop portion 42 for supporting filter elements 33 and 34.

Fig. 5 discloses a modified form of oil conserving apparatus with an oil bath filter therefor. This form is similar to that shown in Fig. l and has many parts in common. The oil conserving apparatus has an inlet and an outlet 111 for normal flow resembling inlet 10 and outlet 11 in Fig. 1 and are provided for the same purpose. The oil bath filter in Fig. 5 is basically the same type of conventional oil bath filter shown in Fig. 1 except for minor structural changes. It has a housing provided with a cylindrical outer wall 112, a cylindrical inner wall 113 and a bottom wall 114. These walls are integral as shown but needv not be, so constructed. A cylindrical coupling tube 115, adapted to be attached to the inlet of the gas compressor, is secured in the bore of the inner wall 113. A cap 116 is provided with a cylindrical depending skirt 117 secured thereto and surrounding an annular filter element 125. A stud 120, secured to an adapter member 118 by a cotter pin 119, is screwed into a threaded hole in the narrow web a, integrally formed in, the coupling tube 115. These members hold the oil bath filter together. The oil bath is normally filled to the: dot-dash line 124 so that the depending skirt 117 forces the. incoming gas to go down through the oil bath before entering the chamber housing the filter element 125. A bafile 1-26- extending upwardly for a short distance from the bottom wall 114- forces the gas to fiow upwardly through the annular filter element 125.

The operation of this oil bath filter is substantially the same as the one. shown in Fig. 1 since the incoming gas enters the oil bathv filter by' the annular passageway provided between the outer wall 112 and the depending: skirt 117, passes through the oil bath and annular filter element 125,. and leaves through the axial passageway provided in the cylindrical inner wall 113 and the coupling.

tube 115.

An oil eliminator means is provided in Fig. 5 in thegas flow path between the oil bath, filter and the inlet 1'10; toprevent oil and finely divided oil spray being: exhausted.

ment 133; a lower filter element 134-, expanded metal discs135; 136, 13.7and1 138; spacer bars 139; washers or spacers: 14.0; fastener member 141; bottom stop 142; stem. 14.3.; win-g, nut 1'44; and cap 146' correspond instructure and purpose to the correspondingly positioned parts in Fig. 1 having reference numerals one hundred less than those in Fig. 5. However, the spacers 139 are secured to expanded metal disc 137 in Fig. 5. A cylindrical retaining sleeve 149 is telescoped into the bore of the intermediate wall 130 to retain the filter element in position. This retaining sleeve has a plurality of equally spaced holes 149a to permit the incoming air to enter the oil conserving apparatus. The oil eliminator means can be lifted off the oil bath filter, separating at the joint 131, 132.

Fig. 5 discloses a bafile means in the flow path between the oil eliminator means and the oil bath filter which corresponds to the baffie means in Fig. 1. This includes the annular bafile 150 with an inwardly and downwardly inclined lip and also includes the surfaces of the housing walls 129, 130 serving as a radially outward extension of baffie 150 and covering the top of the annular passageway between wall 112 and skirt 117. An annular, vertically extending pocket is formed between walls 129 and 130 in said baifie means in vertical alignment with said annular passageway. A depending lip 151 is formed in vertical alignment with the outside surface of the wall 130 on the radially inner side of the pocket to aid in the oil elimination, as will be brought out later. Bafile 150 provides not only the inwardly directed lip but also lip 151 and stop portion 142.

The oil eliminator means (comprising the spaced filter elements 33 and 34 or 133 and 134) in each of the modifications disclosed has a dual purpose.

First, each prevents the oil from the oil bath filter being exhausted through the normal inlet of the oil conserving apparatus during reverse flow. The reverse flow of the gas through these filter elements causes the oil and finely divided oil spray to deposit on the foraminous screen mesh material of which they are composed. The lower filter element (34, 134) having smaller effective flow passages causes the oil spray to build up into oil drops so that it may be easily captured by the larger passageways of the upper filter element if it escapes upwardly. The large oil drops formed on the upper filter element will then fall by gravity back into the oil bath filter below. An air gap or space has been provided between the two filter elements, such as between the filter elements 33 and 34 in Fig. 1, or between 133 and 134 in Fig. 5, to prevent any oil from the lower filter element creeping up the wires into the upper one and out the normal inlet of the oil conserving spparatus during the reverse flow and during the oil elimination operation.

Second, the filter elements of the oil eliminator means pre-filter the gas flowing in the normal direction before it reaches the oil bath filter. Any dirt collected on the wire mesh of the eliminator filter elements will be washed down by the captured oil into the oil bath during reverse flow when the oil eliminator means serves its normal function since both filter elements of each oil eliminator means are of the self-draining type. As previously mentioned, the crimps in Fig. 3 and in Fig. 6 generally extend in the direction of the vertical stream flow and form an acute angle therewith. During reverse flow, the oil in flowing down the wire mesh and along the downwardly inclined crimps will carry the dirt from the pre-filtering operation downwardly off the filter elements down into the oil bath of the oil bath filter. It should be noted that the larger effective flow passages of the upper filter element are ideal for pre-filtering since the incoming air, flowing in the normal direction meets the coarser filter before it meets the finer one. Not only gravity but also the incoming gas, during normal flow, will cause the oil to flow downwardly to carry the dirt from the wire mesh.

In each of the modifications shown, a bafile means is located in the gas fiow passageway between the oil bath filter and the oil eliminator means. It not only prevents the spray of oil emerging through the normal inlet during reverse flow, but also acts as a baflde oil separator for knocking out most of the oil and finely divided oil spray from the carrier gas during reverse flow before the gas reaches the oil eliminator means.

During reverse flow, the gas, laden with oil and finely divided oil spray, leaves the oil bath filter through the annular passageway in Figs. 1 and 5 between the skirt and the outer wall. In each form of the invention, this passageway is straight and extends substantially vertically. At the top of the passageway, there is an abrupt bend in the fiow path caused by the housing or bafile means, and the bafile 50, 150, is located along the inner surface of the larger radius of the bend at the top of the vertical passageway. The baflle lip (downwardly and inwardly depending in Figs. 1 and 5) depends down into the flow path and is located at the portion of the curve nearest in flow communication (in the reverse flow direction) to the oil eliminator means. This structure partially interferes with the direct reverse flow of the gases, and hence, the oil and finely divided oil spray is separated from the carrier gas by being impinged on and collected on the baffle lip by the centrifugal force created by the bend. The structure forms a generally horizontally extending bafile means spaced above and covering the top of the vertical passageway from the oil bath filter. The bafiles 50, 150, each have a deflector portion extending generally in a radial direction and have the aforementioned lip extending downstream therefrom in the reverse flow direction. This lip is inclined downwardly so that any oil descend ing from the oil eliminator means or being impinged on the bafile by the reverse flow of the gases will drain downwardly by gravity toward the oil bath in the oil bath filter. The incoming gas, flowing in the normal direction, will also aid in returning the oil by sucking it downwardly toward the oil bath. Hence, the gas emerging from the normal inlet during reverse flow is substantially free of oil and finely divided oil spray. No fountain of oil emerges from the normal inlet. The oil bath in the oil bath filter is always maintained at substantially the same constant operating level. The baffle means also prevents the fountain of oil from reaching and thoroughly soaking the oil eliminator means. Hence, the baflle means eliminates a great portion of the oil and oil spray from the carrier gas and the spaced filter elements of the dual purpose eliminator means eliminate the remainder.

In the modification shown in Fig. 5 an upwardly extending pocket is formed in the bend of the centrifugal separator portion of the baffle means and is in vertical alignment with the annular vertical passageway from the oil bath filter. In this case, this pocket aids in the elimination of the oil from the carrier gas by serving as a collector pocket therefor. This pocket has a lip 151, as previously described, on its downstream side in the reverse flow direction. The oil collected in the pocket will flow down the walls of the pocket and off the lip and back into the oil bath of the oil bath filter.

In each of the modifications shown, the flow areas are so proportioned that the gas will expand in the oil eliminator means during reverse flow and this expansion will help drop the finely divided oil spray out of the carrier gas. The flow path through the filter elements of the oil eliminator means should have a flow cross sectional area approximately 4 /2 times the flow cross sectional area of the gas path between the oil bath of the oil bath filter and the centrifugal separator bend of the bafile means (annular inlet to oil bath filter between outer wall 12 and skirt 16a in Fig. l or wall 112 and skirt 117 in Fig. 5). This ratio of 4 /2 to l is preferred and gives the best results but a range of 2 /2 to 1 to 6 to 1 is a good practical range and gives satisfactory results.

The operation of each oil conserving apparatus with an oil bath filter, as described, should now be clear. During normal flow when the gas compressor is under load, the gas enters the inlet of the apparatus and is pre-filtered by the dual purpose means (the oil eliminator means),

flows into contact with'the oil bath and through the filter element of the oil bath filter, and then flows out the outlet of the apparatus into the compressor.

When the gas compressor unloads, the gas flows in the reverse direction through the normal outlet of the apparatus, through the oil bath filter wherein it becomes heavily laden with oil and carries with it an upwardly surging fountain of oil, flows upwardlythrough the diverting bend of the centrifugal separator and is collected on either the baffie plate or in the vertically extending pocket, flows through the dual purpose means which new acts as an oil eliminator means and removes the balance of the finely divided oil in the gas and then flows out of the normal inlet of the apparatus. The baffle means including the centrifugal bend and the bafile lip prevent the upwardly surging fountain of oil from the oil bath reaching and thoroughly soaking the oil eliminator means and then emerging from the normal inlet of the apparatus. The bafile lip directs the downward gravity drainage of the collected oil from both the oil eliminator means (dual purpose means) andv the centrifugal separator toward the oil bath filter. The downward flow of the collected oil through the filter elements of the oil eliminator means carries the dirt, previously collected during the pre-filtering operation, downwardly by gravity to the oil bath so that the filter elements will be clean for pre-filtering the next normal flow of gas. The incoming gas, flowing in the normal direction, will also aid in returning the oil in addition to the downward pull of gravity.

Various changes in details and arrangement of parts can be made by one skilled in the art without departing from the spirit of this invention or the scope of the appended claims.

It will be noted in Figs. 3 and 6 that the filter element comprises mesh screen members positioned in the element with all of the parallel crimps positioned at an acute angle to the vertical. Oil is carried upwardly into filter elements 33 and 34 of Fig. l, and into elements 133 and 134 of Fig. 5, during reverse flow. Because of the position of the crimps, oil draining downwardly out of elements 33, 34, 133, 134, carries dirt out the open lower ends of the crimps. Thus these filter elements are self-cleaning.

What we claim is:

1. An oil conserving apparatus with an oil bath filter for the inlet of a gas utilizing device comprising a housing having an annular passageway and an axial passageway, an annular oil bath filter element in a chamber in said housing between said passageways, said annular passageway being a gas inlet for said oil bath filter and the axial passageway being a gas outlet for said oil conserving apparatus and said oil bath filter when said apparatus acts as a filter during normal flow, partition means in said housing compelling fiow from said inlet and through said oil bath filter to said outlet, said housing having an oil eliminator filter unit inlet connected to said oil bath filter inlet by a pasageway, said inlets and outlets having their functions reversed upon reverse flow through said apparatus, an oil eliminator means above said oil bath filter in said last-mentioned passageway, and bafiie means in said last-mentioned passageway between said oil bath filter and said oil eliminator means, said bafile being inclined downwardly to drain toward said chamber, said baifie means having a generally radially extending deflector portion and having a lip portion extending downstream therefrom in the reverse flow direction.

2. An oil conserving apparatus with an oil bath filter for the inlet of a gas utilizing device comprising a housing having an annular passageway and an axial passageway, an annular oil bath filter element in a chamber in said housing between said passageways, said: annular passageway being a gas inlet for said oil bath filter and the axial passageway being a gas outlet for said oil conserving apparatus and said oil bath filter when said apparatus acts as a filter during normal flow, partition means in said housing compelling flow from said inlet and through said oil bath filter to said outlet, said housing having an oil eliminator filter unit inlet connected to said oil bath filter inlet by a passageway, said inlets and outlets having their functions reversed upon reverse flow through said apparatus, an oil eliminator means above said oil bath filter in said last-mentioned passageway, a portion of said passageways between said oil bath filter and oil eliminator means being straight and extending approximately vertically, a generally horizontally extending baffie means spaced above and covering the top of said portion of said passageways, the reverse flow direction in said portion of said passageways being generally vertically upwardly, said bafiie means having a generally horizontal deflector portion extending from above said portion of said passageways in the downstream reversed flow direc tion and a lip on the reverse flow downstream end of said deflector portion, said lip being inclined downwardly and in the general direction of reverse flow.

3. An oil conserving apparatus with an oil bath filter for the inlet of a gas utilizing device comprising a housing having an annular passageway and an axial passageway, an annular oil bath filter element in a chamber in said housing between said passageways, said annular passageway being a gas inlet for said oil bath filter and the axial passageway being a gas outlet for said oil conserving apparatus and said oil bath filter when said apparatus acts as a filter during normal flow, partition means in said housing compelling flow from said inlet and through said oil bath filter to said outlet, said housing having an oil eliminator filter unit inlet connected to said oil bath filter inlet by a passageway, said inlets and outlets having their functions reversed upon reverse flow through said apparatus, a dual purpose means above said oil bath filter in said last-mentioned passageway for preventing oil from said oil bath filter being exhausted through said oil conserving apparatus normal inlet during reverse flow and for pre-filtering the gas flowing in said normal direction to said oil bath filter, said dual means including a filter element of the self-draining type with all passages generally inclined downwardly and wherein the normal flow is from top to bottom so the downward flow of the captured oil will carry the dirt from pre-filtering downwardly ofi said dual means filter element, and bafile means in said last-mentioned passage- Way between said oil bath filter and said dual means partially interfering with direct reverse flow from said chamber to said dual means, said bafile being inclined downwardly to drain toward said chamber.

4. An oil conserving apparatus, as set forth in claim 2, wherein said annular passageway includes the inlet for said oil bath filter and includes said approximately vertically extending portion of said passageways.

5. An oil conserving apparatus, as set forth in claim 2, wherein an upwardly extending pocket is formed in said baflle means in alignment with said approximately vertically extending portion of said passageways.

6. An oil conserving apparatus with an oil bath filter for the inlet of a gas utilizing device comprising a housing having a normal annular inlet passage and an axially extending outlet passage therein, gas normally flowing from said inlet passage through said housing and through said outlet passage into said gas utilizing device, said inlet and outlet having their functions reversed upon reverse flow through said unit, an oil bath filter mounted in said housing in the gas flow path between said inlet and outlet, a dual purpose means above said outlet passage and in the fiow path between said oil bath filter and said inlet for preventing oil from said oil bath filter being exhausted through said normal inlet during reverse flow through said apparatus and for pre-filtering the gas flowing in said normal direction to said oil bath filter, a transverse partition in said housing between said dual 9 10 purpose means and said outlet passage and closing the References Cited in the file of this patent spacedradially lijnwatrcllJ ofd said agnfiiilar inlgt bpassage and1 UNITED STATES PATENTS plOVl mg an a rup en in sa1 ow pa e ween Sal oil bath filter and annular passage and said dual means g g 1938 upon said reverse flow, and a baflle lip between said dual 5 2243323 6 at a e purpose means and said partition extending into said flow 2286479 F a ton path and being inclined downwardly along the larger 2391887 5""21 g radii of said bend and at the portion of said bend nearest Son 6 a 2,570,623 Wlslor Oct. 9, 1951 in flow communication to said dual means, whereby during reverse flow a large portion of said oil is removed 10 FOREIGN PATENTS from the gas before it reaches said dual means by being 550 292 Great Britain Jan 1 4 impinged and collected on said baflle lip by the cen- 657,724 Great Britain Sept. 26, 1951 trifugal force created by said bend. 976,751 France Mar. 22, 1951 

